1. Field
This disclosure relates generally to semiconductor device manufacturing, and more specifically, to the manufacture of non-volatile memories having a split gate.
2. Related Art
Non-volatile memories (NVMs) have many important uses in combination with other circuitry, especially when electrical power is not present. The use of non-volatile memories is particularly advantageous for power savings applications or when power is interrupted. Primarily, NVMs are implemented by using floating gate transistors, but floating gate transistors have limitations, especially as geometries have gotten smaller. If there is any current leakage path, regardless of how localized, to the floating gate, stored electrical charge can be completely removed from the floating gate. Thus, nanocrystals and nitride as the storage layer have become of more interest because one leakage path does not discharge the entire storage layer. One of the structures that has been shown to have much promise for programming efficiency is a split gate memory cell using source side injection in which both a control gate and a select gate influence the channel but only the control gate ever has the higher voltage needed for programming and erasing.
Known split-gate memory cell devices use two gates. A first gate is a control gate to control the program and erase operations. A second gate is a select gate to select when the memory bit is to be programmed. Such known split-gate memory cells are therefore bigger than single gate memory devices. Therefore, it is difficult to reduce dimensions of the structures that are used to implement known split-gate memory cells to take advantage of improvements in processing technology.